whats inside an hard disk!

2008-02-06T05:10:00.000-08:00

The other day a friend of mine gave me an old SCSI hdd. It had gone bad. I had always wanted an external Hdd. So i went to lamington road the tech heaven of mumbai to buy me some "converter" thingy and an external hdd housing. i found that there were not many such converter things available and those available were so costly that i could buy a brand new external pocket hdd such as transcend storejet 2.5 at the same price.
I tried selling the HDD to the second hand computer parts vendors lining the pavements of lamington road.None of these computer vendors seemed interested in my HDD.I guess that's because home pcs seldom use scsi drive al though its widely used in servers.I came back home with a cheap chinese made torx srewdriver set which i got for cheap there.
I had no option but to throw away the hdd since nobody would buy it. I thought of opening the hdd before i could let the hdd rest in peace.
The hdd was an old 18.64 Gb seagate barracuda.

The HDD had 7 T5 sized torx screws on the top side. and 7 on the PCB side.

The LCT spindle chip burnt out when i was fiddling with the hdd.i tried powering it directly from a laptop charger,an old power supply of a lexmark printer!!! notice the dent on the chip!!
I started by removing the pcb mounting screws.to unmount the pcb from the hdd body.

The various components on the pcb of the Hdd are as follows.Notice that the only contact between the hdd and the pcb is made by spring contacts there are no soldered contacts asone might have guessed!!

These are all the components i could identify since i'm just a newbie.

Data contacts connect the main unit to the pcb all the data transfer takes place through these pins. The spindle motor is a special type of a stepper motor . Unlike steppers wich has 2 coils its actually a"brushless" three-phase motor driven by three phase current.The lct spindle chip drives the motor.The motor has 3 coils .Each driven by 3 sine waves 120 degrees out of phase.thus the motor runs on analog waveform rather than digital steps as in stepper motors.

Now for the label side of the HDD

The last screw hide below the label.

The label side with all screws removed.

At last let's see whats inside!!!

This is the heart of the hard disk the platter is mounted on the spindle motor by means of the 6 torx screws. the head skims just a few micrometers over the platter almost touching the platter.

The head should not touch the platter surface or else the disk surface will get scratched and the hard disk will be rendered useless. The motion of the spindle motor is very smooth. this is done in order to reduce platter vibrations so as to prevent any damage to the disk surface.this smooth mition of the motor is acheived by means of ball bearings. now-a-days fluid bearing is used which give a smoother motion.the fluid bearing is usually used in high-end hard drives.

The head movement assembly moves the head to the position where the data is stored this is a stepper motor.The motor is made up of a coil attached to the arm.this coil lies between the extremly strong magnets.when current is applied to the coil the coil moves causing the arm to move. the movement of the arm is proportional to the signal applied hence it forms a stepper.By applying the right amount of current the arm movement can be controlled very accurately so as to move the head to the appropriate position where the data is stored.

The magnets are usally very strong noedymium magnets.

a small pack containing some type of dusst capturing substance is placed at on corner. this pack would have turned black if any particles would have flung off the disc.

The metal supports carrying the head are very flexible and delicate. here's a closeup of the head

there are two heads one for each side of the platter.The usual data density of the platter is 10Gb per platter/side.
the head assembly has of an ic on board.sorry for the blurry image i will upload a better image as soon as possibleThe platter is fixed upon the spindle by means of 6 torx screws and washers.

http://www.youtube.com/watch?v=4Ait9BUTKkA

what's inside a hard disk drive

whats inside an hard disk!